The present invention is based on a fuel injector-spark plug combination.
A fuel injector including an integrated spark plug is described in European Published Patent Application No. 0 661 446. The fuel injector with the integrated spark plug is used for the direct injection of fuel into the combustion chamber of an internal combustion engine and for igniting the fuel injected into the combustion chamber. By the compact integration of a fuel injector with a spark plug, it is possible to save installation space at the cylinder head of the internal combustion engine. The conventional fuel injector with integrated spark plug includes a valve body which, together with a valve-closure member able to be actuated by manner of a valve needle, forms a sealing seat, adjacent to which is a spray-discharge orifice, which discharges at an end face of the valve body facing the combustion chamber. A ceramic insulation element insulates the valve body from a housing body in a high-voltage proof manner, the housing body being able to be screwed into the cylinder head of the internal combustion engine. Located on the housing body is a ground electrode in order to form an opposite potential to the valve body acted upon by high voltage. In response to a sufficiently high voltage being applied to the valve body, a spark arc-over occurs between the valve body and the ground electrode connected to the housing body.
This conventional fuel injector with the integrated spark plug provides that the position of the spark arc-over is not defined with respect to the fuel jet spray-discharged from the spray-discharge orifice, since the spark arc-over may occur at just about any location in the lateral region of a valve-body projection. With this configuration, a reliable ignition of the so-called jet root of the fuel jet spray-discharged from the spray-discharge orifice is not possible with the necessary reliability. However, a reliable and temporally precisely defined ignition of the fuel jet is absolutely required for reduced emissions. Furthermore, the exit orifice of the fuel jet may be subject to continually worsening carbon fouling or coking, which affects the form of the spray-discharged jet. The ceramic extrusion coat is relatively cost-intensive.
The fuel injector-spark plug combination according to an example embodiment of the present invention may provide that, by positioning the fuel injector and the spark-plug insulator of the spark plug in a shared connecting member, which may be arranged at an end face of the cylinder head of the internal combustion engine, the components may be optimally arranged relative to each other, resulting in a system that is easy to install and requires little space.
The spark-plug insulator may be secured in the housing by a threaded sleeve, the spark-plug insulator being screwed into the mounting support.
Tilting of the longitudinal axis of the spark-plug insulator relative to the longitudinal axis of the fuel injector may prevent the spark plug from being directly exposed to the fuel jet spray-discharged from the fuel injector.
Moreover, the spark plug and the ground electrode of the spark plug may each be exchangeable independently of the fuel injector.
The housing may be made of plastic and may be produced in an inexpensive manner.
An example embodiment of the present invention is represented in the drawing in schematic form and explained in greater detail in the following description.